There are many wire ropes. It is well known that when a wire rope is used, unless a wire rope is adapted to an object thereof and a place of use is selected, an advantage provided by a wire rope cannot sufficiently be utilized.
Particularly, a wire rope for a running wire in a crane or the like is bent by a sheave and is wound to a drum. Therefore it must have an adequate fatigue resistance.
A rope of this kind is known in the prior art, as shown by FIG. 1. It has a plurality of pieces of side strands ST at an outer periphery of a core rope CR to be twisted, and a fiber core or a metal core is used for the core rope. Because of this structure, metal contact is unavoidable between the strands, and between a sheave portion and the rope thus causing wear of the rope.
Although a number of ropes have been proposed as a countermeasure thereagainst in the prior art, problems posed by the respective prior arts cannot be construed as sufficiently resolved.
According to Japanese Patent No. 2876140 (Prior Art 1), a core rope is thinly coated with a resin while wear between the core rope and a side strand can be avoided, wear between and at a contact face with a sheave cannot be avoided.
It is described in Japanese Patent No. 3493248 (Prior Art 2) that a spacer made of a resin is provided between side strands and an angle of an apex of the spacer is 60 degrees as considered in an outer peripheral direction. However a base end portion of the spacer is formed by a wedge-like shape, the wedge portion reaches a center of the rope, and therefore, an effective sectional area of the rope is reduced so that it is difficult to use the rope for an application that involves a high breaking load.
JP-B-63-46196 (Prior Art 3) discloses a filling member forming a diverging portion by a constriction with a front end having a fan-like shape and interposed between side strands. However, a reinforcement core is provided for a filling material, and therefore the filling material does not extend between wires constituting the side strand. Also, when the reinforcement core is disconnected at an early stage, there is a possibility of jumping out the reinforcement core from the filling material. Furthermore, since the reinforcement core is provided for the filling material, a special equipment is needed for fabrication thereof at increased cost.
U.S. Pat. No. 6,360,522 (Prior Art 4) discloses a rope that is similar to the rope of Prior Art 3. A spacer is formed with a diverging portion by a constriction with a front end of a fan-like shape oriented between side strands. However, here a resin having a high strength of a biaxially oriented molecular structure or the like is used, and therefore, the spacer is difficult to be deformed and does not extend between wires constituting a side strand. Therefore the wire can move and a wire breakage at a point of contact with a core rope cannot be restrained and elongation of the rope is increased.